We and others have discovered that S100B is not just a clinical marker, but that it binds to p53, dissociates the p53 tetramer, and down-regulates p53 protein levels and function in malignant melanoma. The goal of this project is to inhibit the S100B-p53 interaction and restore wt p53 protein levels in this cancer. Computer aided drug design (CADD), NMR, thermodynamic binding, and p53 functional assays will be used to discover lead compounds that bind to the p53 site on Ca2+loaded S100B and inhibit the S100B-p53 interaction. The SAR (structure/activity relationship) by NMR approach and DOCKING protocols will also be used to find compounds that bind other site(s) on Ca2+S100B, which are proximal to the p53 binding site. 3D characterization of S100B-drug complexes will be performed using NMR spectroscopy and X-ray crystallography. This will include structure determinations of new complexes discovered and several existing S100B-drug complexes (S100BKD<10 ?M) that inhibit the S100B-p53 interaction in vitro and in primary malignant melanoma cells. Compounds that inhibit the S100B-p53 interaction will be optimized to bind S100B more tightly via chemical modifications. Organic syntheses will be guided by 3D structural data and CADD lead optimization approaches. Testing of such analogues will be done using NMR, competition binding studies, and biological. As a new Aim, which is the topic of this competitive revision, will be to do in vivo testing of promising compound for their ability to suppress/eliminate tumors in melanoma mouse models. Such work will be done in collaboration with Dr. Danna Zimmer at the Texas A&M School of Veterinary Medicine. These in vivo data will be critically important first by helping us focus our design/synthesis efforts only on lead compounds or classes of compounds that have efficacy in vivo. Additionally, these data are absolutely necessary to set priorities for which compounds to pursue in human clinical trials. We will hire 2 new technicians to complete these studies as well as provide work for numerous employees at several facilities at both the University of Maryland and at Texas A &M. PUBLIC HEALTH RELEVANCE: The ongoing project (CA197331) as well as the new work proposed in this competitive revision application addresses many important public health concerns including providing drugs to treat several cancers including malignant melanoma. This work also provides general principles for inhibiting protein-protein interactions, which is at the forefront of drug-design challenges.